Electronic structure and spectroscopy of O2 and O2+

We carried out a comprehensive SCF MRD--CI ab initio study of the electronic structure of O$_2$ and O$_2^+$. Potential energy curves (PECs) of about 150 electronic states of O$_2$ and about 100 of O$_2^+$, as well as a number of states of O$_2^{++}$ were computed. The cc--pVQZ basis set augmented with diffuse functions was employed. Spectroscopic parameters ($T_e, T_v, \omega_e, \omega_ex_e, B_e,$ $D_e, D_0$, $\mu$, IP, etc.) are reported. A preliminary sample of the results will be presented. The electronic absorption spectrum of O$_2$ has proved difficult to analyze/interpret due to the unusually large number of electronic states which arise from the peculiar open--shell structure of both the oxygen atomic fragments and the O$_2$ molecule. For instance, there are 62 valence molecular electronic states which correlate to the six lowest dissociation limits resulting from the three valence O atom fragment states ($^3$P, $^1$D, $^1$S). In addition, there are several $nl\lambda$ Rydberg series converging to the X$^2\Pi_g$ ground ionic state and to the lowest two excited states of the cation, a$^4\Pi_u$$_i$ and A$^2\Pi_u$. Furthermore, a number of interactions of various types among several electronic states result in rovibronic perturbations which manifest themselves, e.g., as irregular vibronic structure, hence severely complicating the assignment of the absorption features and the analysis and interpretation of the spectrum. An overview of the electronic states and spectroscopy of O$_2$ will be presented. A chief motivation of this study of O$_2$ was to try to provide a theoretical insight on the nature, energetic position, shape, and dissociation asymptotes, of electronic states located in the 4 eV energy region encompassed between the O$_2^+$ ground state X$^2\Pi_g$ (IP$=12.07$ eV) and the first excited state of the cation a$^4\Pi_u$$_i$ (IP$=16.10$ eV). This in order to aid in the interpretation of experimental data related to the mechanism(s) of the neutral dissociation of the O$_2^{**}$ (Rydberg) superexcited states, which competes with autoionization. We are currently striving to compute PECs of relatively highly excited states of O$_2$ located in the 12--16 eV energy region which might help to visualize possible pathways for the neutral XUV photodissociation of the I, I$^{\prime}$ and I$^{\prime\prime}$ $^3\Pi_u$ superexcited states of O$_2$ leading to the O($^3$P) + O$^{*}$($^3$S, $^5$S) dissociation limits.Ope

Differential effects of selective inhibitors targeting the PI3K/AKT/mTOR pathway in acute lymphoblastic leukemia

Purpose: Aberrant PI3K/AKT/mTOR signaling has been linked to oncogenesis and therapy resistance in various malignancies including leukemias. In Philadelphia chromosome (Ph) positive leukemias, activation of PI3K by dysregulated BCR-ABL tyrosine kinase (TK) contributes to the pathogenesis and development of resistance to ABL-TK inhibitors (TKI). The PI3K pathway thus is an attractive therapeutic target in BCR-ABL positive leukemias, but its role in BCR-ABL negative ALL is conjectural. Moreover, the functional contribution of individual components of the PI3K pathway in ALL has not been established. Experimental design: We compared the activity of the ATP-competitive pan-PI3K inhibitor NVP-BKM120, the allosteric mTORC1 inhibitor RAD001, the ATP-competitive dual PI3K/mTORC1/C2 inhibitors NVP-BEZ235 and NVP-BGT226 and the combined mTORC1 and mTORC2 inhibitors Torin 1, PP242 and KU-0063794 using long-term cultures of ALL cells (ALL-LTC) from patients with B-precursor ALL that expressed the BCR-ABL or TEL-ABL oncoproteins or were BCR-ABL negative. Results: Dual PI3K/mTOR inhibitors profoundly inhibited growth and survival of ALL cells irrespective of their genetic subtype and their responsiveness to ABL-TKI. Combined suppression of PI3K, mTORC1 and mTORC2 displayed greater antileukemic activity than selective inhibitors of PI3K, mTORC1 or mTORC1 and mTORC2. Conclusions: Inhibition of the PI3K/mTOR pathway is a promising therapeutic approach in patients with ALL. Greater antileukemic activity of dual PI3K/mTORC1/C2 inhibitors appears to be due to the redundant function of PI3K and mTOR. Clinical trials examining dual PI3K/mTORC1/C2 inhibitors in patients with B-precursor ALL are warranted, and should not be restricted to particular genetic subtypes

Measuring velocity of sound with nuclear resonant inelastic x-ray scattering

Nuclear resonant inelastic x-ray scattering is used to measure the projected partial phonon density of states of materials. A relationship is derived between the low-energy part of this frequency distribution function and the sound velocity of materials. Our derivation is valid for harmonic solids with Debye-like low-frequency dynamics. This method of sound velocity determination is applied to elemental, composite, and impurity samples which are representative of a wide variety of both crystalline and noncrystalline materials. Advantages and limitations of this method are elucidated